The fibre channel is a serial data communication network architecture and protocol for interconnecting computers and peripheral devices. The fibre channel supports several protocols, including the Small Computer System Interface (SCSI) protocol, an ANSI standard for controlling peripheral devices by one or more host computers. The computer or peripheral devices are connected to the network through fibre channel ports or other means. The host contains the fibre channel port. The fibre channel port uses a local data bus, such as a peripheral computer interface (PCI) bus, to implement data transfers.
Because the high bandwidth and connection flexibility it offers, fibre channel is often used for connecting peripheral devices within multi-disk drive enclosures, such as redundant arrays of inexpensive disks (RAIDs), and for connecting multi-disk drive enclosures with one or more host computers. These multi-disk drive enclosures offer great economy, greater storage, and redundancy that improve operational reliability.
Malfunctioning enclosures can, in certain cases, degrade or disable communications. There is the possibility of inserting a disk drive that is incapable of operating at the speed its enclosure has established for its remaining drives. There are no physical limitations which would prevent this event from occurring.
In the prior art, it is up to the enclosure services component to detect that the drive is not communicating properly and effectively remove it from the fibre loop by asserting its bypass control line. This has the effect of presenting information that indicates that the drive has failed without any indication that the reason the drive has failed is only because of its mismatched speed.
Therefore, it would be desirable to provide a method for changing disk drive speeds in a controlled manner. It would also be desirable to provide such a method with simplified circuitry.